Strategies for preventing oven fires

Bakers don’t set out to be the cautionary tale. They don’t invite calamity to visit, either, but that’s just what talking about a fire prevention plan feels like, especially when a critical piece of equipment — the oven — functions like an inherent recipe for disaster. Sure, all the necessary components for fire might be found in the oven at one point or another, but as any baker knows, it’s all about how you put the ingredients together.

“People hear ‘oven fire’ and think of a Hollywood-style explosion,” said Ondrej Nikel, director of engineering, Topos Mondial Corp. “You should have a healthy fear because you need to respect the oven. But if you keep them maintained, they are very reliable and quite safe.”

With good best practices, SOPs and open dialog with suppliers, bakers can avoid disaster that could result in loss of equipment, the facility or even a life.

Identify, eliminate risks

Commercial ovens have come a long way since the “­olden” days when bakers would have to ignite them with a wad of paper or cloth.

“Today, ovens are extremely safe, but if good operation procedures are not enforced, the potential for fire still exists,” said Dennis Kauffman, director of thermal products, AMF Bakery Systems. A baker must clearly understand where the risks lie and how to eliminate those factors.

The first step for identifying fire hazards, especially when purchasing a new oven, is open communication with the supplier.

“The oven manufacturer certainly needs to be aware of any obvious combustibles that the baker may intend to put in the oven,” Mr. Kauffman said. “Some examples are parchment paper, openable cardboard pans, high-fat products and other such items.”

He noted that this information helps oven manufacturers recognize if a baker is requesting an oven temperature that might be too high for what’s going into it.

Obviously, the supplier needs all the product specs to properly design the oven, but these details can also lead to fire safety.

“We want to know how a product is made up and what the ingredients are,” said Nathan Stockton, sales manager, CH Babb. “Oven manufacturers are aware of the different grades or areas where there’s more likelihood to produce a risk of fire, so if you have a meat-based product that’s wrapped in dough, and it leaks out fats from the meat, we need to know how much oil is going to be in the pan or on the hearth.”

Additionally, Reading Bakery Systems (RBS) encourages bakers to test products in its Science & Innovation Center so the company can gain a deeper understanding of all the caveats specific to each product.

For good fire prevention, product specs — streusel on top or cornmeal underneath — must not be overlooked.

Flash point and autoignition are also important factors in gauging the risk of an oven fire. If the flash point is the temperature where, given assistance, a fire can start, what’s going to assist it? Along with the heating source itself (which is hard to eliminate in an oven), fire needs a material or gas to sustain combustion, and it needs oxygen.

“The most common causes in our industry are loose, dry materials that have fallen off the band and built up inside,” said Kevin Knott, technical sales manager, Franz Haas Machinery of America.

Mr. Stockton also suggested that bakers should think beyond just flammability of a product or material and consider how it catches fire once it reaches the flash point, which requires a source such as a flame, or autoignition (also known as spontaneous combustion).

“We’ve done some experiments in our test lab where we pile up bread chips … if you heat them to a certain point over time, it’s sort of like having a pile of grass in your yard,” he explained. “When you put your hand into the middle, it’s actually hotter inside than it is on the surface. What happens is that the center heats up and reaches that autoignition point.”

Flour is a necessity for so many baked foods, but the dust also comes with risk of explosion in many areas of production, including the oven.

“This is due to the inherent vacuum of an oven chamber pulling in surrounding ambient air,” said Scott McCally, president, Auto-Bake, part of the Middleby Bakery Group.

He suggested that in any area where flour migration is possible, explosion-proof rated electrical devices should be installed.

Oil, another necessary element to the baking process, is also a fire hazard. A failure in the transportation system or heat exchanger can cause oil or other thermal fluid to escape into the baking chamber of an indirect-fired thermal oven. When that happens, a fire can start — even without a spark — if the oil reaches the flash point during depressurization, said Mr. McCally.

“Degradation of the thermal fluid either from oxidation, which results in sludgy oil, or overheating, which results in thin oil, can greatly reduce the flash point temperature and increase the inherent hazard of deflagration during an oil leak,” he explained.

Eliminate the mess, mitigate the risk

Once a baker understands where the risks lie, it should be easy to practice good fire prevention. But that is sometimes easier said than done. Increased and rapidly changing customer requirements often leave little time for planning and prevention for the sake of getting the product out the door.

Think of the basic practice of avoiding clutter: Clean up the small messes regularly, and you won’t have to contend with a huge one. This could be the golden rule for fire safety in the oven, but it’s one that can be hard to keep in play.

“People are running their product more often because of the requirements to go faster and have more uptime,” Mr. Stockton suggested.

Because of this, bakers want ovens that can be easier to clean and that also reduce downtime.

For ovens with stainless-steel construction, clean-in-place (CIP) is a critical feature for food safety, but it’s also become important for fire prevention.

“We are getting more requests for CIP and large access doors,” Mr. Stockton said, noting that stainless-steel construction of fully welded ovens is also top of mind. “They want to wash it down with a hose and have a slant to a drain.”

Oftentimes, bakers will use a pressure washer to clean out the oven, and a CIP system may not be necessary. For Haas it’s about access, and that means more — and larger — doors.

“In older ovens, you would get in there and scrape the materials out, but the door made it difficult,” Mr. Knott explained. “We spent a lot of time redesigning the physical wall so you can have a smooth, hot surface to rake that material out. We keep making bigger doors and better access so bakers can physically take tools and get inside to clean out underneath the pressure chambers.”

Features that keep the band clean are an option for preventing buildup of crumbs and other debris. For example, RBS ovens are designed with brushes and burn-off sections for its bands.

“Typically, the belt is burned off with a series of burners, and then the belt is brushed to knock off any carbon residue,” said Tremaine Hartranft, director of engineering, RBS. “Depending on the product, there are cases where the belt is brushed both before and after the burn-off section.”

It’s important to clean out debris early. For example, the J4 oven, which Topos distributes in the United States, was designed so that cornmeal or other such particulates cannot build up in the baking chamber.

“The oven hearth belt drags the cornmeal out to the end,” said Damian Morabito, Topos president and c.e.o. “The cornmeal is drug out from the baking chamber and from the return path, and then it is all collected in catch pans at the terminal ends of the oven.”

When the belt completely drags on the baking and return surfaces in this manner, it almost completely prevents debris from building up in the hot baking chamber and belt return path where fires typically begin.

Haas uses a combination of burners and brush cleaners to remove belt residue.

“We’ve used ultrasonic air knives to blow the ‘ash’ off the belt,” Mr. Knott said.